Water Use for Agriculture in Priority River Basins – Section 5 Australia The Murray-Darling Basin 1 Water Use for Agriculture in Priority Rivers Basins Section 1 Executive Summary Introduction Water Resources – A Global Perspective Section 2 Africa: – Niger River Basin – Lake Chad Basin – Zambezi River Basin Section 3 South Asia: – Indus River Basin Section 4 East Asia and the Pacific: – Mekong River Basin – Yangtze River Basin Section 5 Australia: – Murray-Darling Basin Section 6 Europe and Central Asia: – Great Konya Basin Section 7 North and Middle America: – Río Grande Basin Section 8 Main Conclusions Literature cited in the study
Transcript
Water Use for Agriculture in Priority River Basins – Section 5 AustraliaThe Murray-Darling Basin
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Water Use for Agriculture in Priority Rivers Basins
Section 1 Executive SummaryIntroductionWater Resources – A Global Perspective
Section 2 Africa:– Niger River Basin– Lake Chad Basin– Zambezi River Basin
Section 3 South Asia:– Indus River Basin
Section 4 East Asia and the Pacific:– Mekong River Basin– Yangtze River Basin
Section 5 Australia:– Murray-Darling Basin
Section 6 Europe and Central Asia:– Great Konya Basin
Section 7 North and Middle America:– Río Grande Basin
Section 8 Main ConclusionsLiterature cited in the study
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CONTENTS
1 The Murray-Darling Basin ..................................................................................................... 31.1 Management of the Murray-Darling Basin ................................................................. 3
1.1.1 Conflicts in the basin........................................................................................... 31.1.2 The management dilemma .................................................................................. 31.1.3 The Murray-Darling Basin Agreement ............................................................... 41.1.4 National Action Plan for Water Quality and Salinity ......................................... 5
1.2 Features of the Murray-Darling Basin ........................................................................... 51.2.1 Ecoregions in the Murray-Darling Basin ............................................................ 51.2.2 Climate and water resources ............................................................................... 61.2.3 Surface water resources ...................................................................................... 71.2.4 Water diversions and storage .............................................................................. 9
1.3 Agriculture..................................................................................................................... 91.3.1 General agriculture versus commodity approach................................................ 91.3.2 Geographic perspectives in the Murray-Darling Basin..................................... 11
1.4 Irrigation and drainage development ........................................................................... 121.4.1 Irrigation methods ............................................................................................. 121.4.2 Environmental impacts on water diversions and storages ................................ 14
1.5 Land use....................................................................................................................... 151.5.1 Erosion rate and sediment ................................................................................. 161.5.2 Nutrient loading ................................................................................................ 161.5.3 Salinity .............................................................................................................. 181.5.4 Economic and social impacts ............................................................................ 191.5.5 Future of irrigation ............................................................................................ 20
2 Conclusions for the Murray-Darling Basin........................................................................ 222.1 Irrigated agriculture ..................................................................................................... 222.2 Future water demand ................................................................................................... 23
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1 THE MURRAY-DARLING BASIN
The Murray-Darling Basin contains the majority of irrigated agriculture in Australia. The purposeof this chapter is to determine the country’s high-priority irrigation commodities in terms of theenvironmental impact they generate. The chapter commences with an outline of managementsystems within the basin, setting a context for an analysis of the basin’s characteristics, theagriculture within it, and the environmental problems associated with it. There are somesignificant differences between the northern and southern parts of the basin which are alsorelevant to a decision about future priorities. Further, there are some significant issues in relationto commodities outside the Murray-Darling Basin and, in determining Australian priorities, thesemust also be considered.
Past management practices, which have led to unsustainable land and water use, and currentpractices, which focus on achieving sustainability, provide an essential context for determiningpriority crops on which to focus this study. The biophysical characteristics of the basin are alsopresented. These reveal the inherent difficulty of applying European-style water use practices in avery different geological and hydrological setting. The attempt to harness water resources inAustralia has led to a particular type of agricultural use and this in turn has led to a huge range ofenvironmental problems.
Located in the south-east of Australia, the Murray-Darling Basin covers 1,061,469km2,equivalent to 14 per cent of the country’s total area. East-west, the basin extends 1,250km, fromthe most easterly point near Warwick to the most westerly, north-west of Goolwa. From thesource of the Warrego River in the north to the headwaters of the Goulburn River in the south –from 24°S to almost 38°S in latitudinal terms – the distance is some 1,365km.
1.1 Management of the Murray-Darling Basin
1.1.1 Conflicts in the basin
Conflicting social, environmental, economic and political issues are at play when discussingwater management in the Murray-Darling Basin. One of the most pressing issues in the basin is,and will continue to be, the resolution of conflicts between different users competing for thelimited quantities of fresh water. There has been a history of conflict over water resources inAustralia since European settlement, arising from the different, competing values which haveunderpinned water resource management policies. These competing values have manifestedthemselves in conflicts between stakeholders; for example, the construction of dams in catchmentareas used for stock, the downstream needs of agriculture versus the needs of urban and industrialcentres, and competition for water between the recreation and tourism sector and those favouringconservation of water resources for regenerative processes.
1.1.2 The management dilemma
Central to the problems of water management in the catchment is the inherent conflict between anational hydrological system and a political/administrative system, the boundaries of which donot coincide. The inter-jurisdictional nature of the Murray-Darling River has long compoundedconflicts over water. The basin extends over three-quarters of the state of New South Wales, morethan half of Victoria, significant portions of Queensland and South Australia, and includes thewhole of the Australian Capital Territory. The tributaries of the Darling form part of the border
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between Queensland and New South Wales, while Victoria lies on the southern bank of theMurray River. These are critical factors in any examination of the management of the basin.
Although there are no language barriers between the different jurisdictions charged withmanaging land and water resources, there are significant challenges in generating cooperativeapproaches. The need for cooperation was recognized early in the development of the Australianfederation.
Table 1.1 State shares in the Murray-Darling Basin
State Total surfacearea(km2)
State area in basin(km2)
% of state areain basin
% of total riverbasin
New South Wales 802,081 599,873 74.79 56.51Victoria 229,049 130,474 59.96 12.29Queensland 1,776,620 260,011 14.63 24.50South Australia 984,395 68,744 6.98 6.48Australian Capital Territory 2,367 2,367 100.00 0.22Total 3,794,512 1,061,469 100.00
1.1.3 The Murray-Darling Basin Agreement
In 1984, a Parliamentary Select Committee was convened to examine the management of thebasin. The committee’s final report, Salt of the Earth, concluded that salinization was worseningrapidly, affecting productivity and the economic viability of irrigation in the basin. Between 1985and 1987 there were countless meetings of ministers responsible for water, land andenvironmental resources to negotiate a new agreement. The outcome was the Murray-DarlingBasin Agreement, signed by the Commonwealth Government, New South Wales, Victoria andSouth Australia. Queensland became a signatory in 1996, with the Australian Capital Territoryjoining in 1998. The preamble to the agreement states that “the Commonwealth, New SouthWales, Victoria and South Australian governments wish to promote and coordinate effectiveplanning and management for the equitable, efficient and sustainable use of water, land andenvironmental resources of the Murray-Darling Basin”. The agreement created a three-tieredadministrative body, comprising the Murray-Darling Basin Ministerial Council (MDBMC), theMurray-Darling Basin Commission (MDBC), and the Community Advisory Committee.
One major success of the agreement has been the implementation of a comprehensive planningframework for the basin by the MDBC. In 1990, a Natural Resource Management Strategy wasadopted by the MDBMC. The strategy established two fundamental ‘pillars’ for handling naturalresource management in the basin. The first was the philosophy of integrated catchmentmanagement, recognizing the linkages between various biophysical processes, which affect or areaffected by water, its movement and its uses. The second ‘pillar’ was the community/governmentpartnership, recognizing that neither party working in isolation can protect the basin’s naturalresources. In 1999, the MDBC commenced the development of a new integrated catchmentframework for the period 2001–2010. The framework recognizes the complex interrelationshipbetween the condition of land and water resources and human activities and pursuits, and thatland management and use affects the quality and quantity of the catchment’s water resources. Asa consequence, water resource planning must take full account of the variety of natural factorsand features and the human influences on the environment.
Despite some progress in implementing water reforms, there is a realization that the health of theriver basin has continued to decline in many areas, with ongoing threats to a number of species.
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There has also been national recognition of the need to inject significant additional investment ifsustainable land and water management is to be achieved.
1.1.4 National Action Plan for Water Quality and Salinity
As a result of past poor land management practices, a hydrological imbalance in the basin hasbeen created resulting in salinization, increased turbidity, nutrient levels, bacterial pollution andpesticides. This is threatening the biological diversity, environmental health and productivity ofmany regions. Faced with estimates that it will cost AU$46 billion over ten years to overcome theproblem of salinity, the federal government has launched a AU$700 million package entitled ‘OurVital Resources: National Action Plan for Salinity and Water Quality in Australia’. The plan wasannounced in October 2000, however its arrangements are still being determined, withconsiderable uncertainties as to how the money will be delivered and targeted towards outcomes.
1.2 Features of the Murray-Darling Basin
1.2.1 Ecoregions in the Murray-Darling Basin
There are three WWF Global 200 ecoregions situated in the Murray-Darling Basin: EasternAustralia Temperate Forests, Southern Australian Mallee and Woodlands, and Eastern AustraliaSmall Rivers and Streams.
Eastern Australia Temperate Forests The generally more moderate climate and high rainfall of south-eastern Australia give rise tounique eucalyptus forests and open woodland dominated by acacia trees. The region served as arefuge when drier conditions prevailed over most of the continent. Consequently, it has aremarkable diversity of plants and animals with high levels of regional and local endemism.Species include koala (Phasolarctos cinereus), golden-headed flying fox (Pteropuspoliocephalus), squirrel glider (Peterus norfolcensis), and wombat (Vombatus ursinus). Forests ofmountain ash (Eucalyptus regnans) provide habitat for the endemic Leadbeater’s possum(Gymnobelideus leadbeateri). Birds include endemic species such as Albert’s lyrebird (Menuraalberti) and russet-tailed thrush (Zoothera heinei), as well as a vast number of wider-rangingspecies like black-necked stork (Ephipiorhynchus asiaticus), Australian king-parrot (Alisterusscapularis), and yellow-tailed black-cockatoo (Calyptorhynchus funereus).
General threats: Much of the pre-European settlement vegetation in this ecoregion has sufferedfrom historical conversion of forests to any of a number of uses: suburban/urban centres,livestock production, agriculture, and timber production, among others. With the exception ofsouth-western Australia, this is the most heavily altered area on the continent. Invasive plant andanimal species are numerous and problematic throughout the ecoregion, while increased growthof suburban and urban areas, alteration of natural disturbance regimes, and grazing are continuingthreats.
Southern Australian Mallee and WoodlandsThis ecoregion is one of only six Mediterranean shrubland complexes in the world. Although notas rich as the nearby Mediterranean shrublands of south-western Australia, these woodlands areextremely diverse, supporting an array of plant and animal wealth. Native plant communitiesinclude those dominated by mallee (Eucalyptus diversifolia) which are distributed along coastaldunes and swampy areas dominated by species of Gahnia. Other dominant plants includeMelaleuca lanceolata and Hakea rugosa, in addition to numerous herbaceous species such as
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morning flag (Orthrosanthus multiformis), desert baeckea (Baeckea crassifolia), and silveryphebalium (Pheballium bullatum). Among numerous birds species with the smallest ranges arethe firetail (Stagonopleura bella), skylark (Alauda arvensis), little raven (Corvus mellori),Gilbert’s whistler (Pachycephala inornata), and the endemic red-lored whistler (P. rufogularis).
General threats: Much of the native vegetation in this ecoregion has been cleared for agricultureor for grazing. Today, portions of the ecoregion are managed for commercial forestry, includingsome public lands.
Eastern Australia Small Rivers and StreamsBoth species richness and endemism are high in eastern Australia’s streams, in contrast to streamsin western regions. South-east Australia has a particularly species-rich and endemic crayfishfauna (family Parastacidae), as well as a large number of endemic freshwater fish. The rivers,lakes and springs of this ecoregion contain numerous relict species, including many species ofdragonflies (Odonata) and mayflies (Ephemeroptera). The most famous resident of easternAustralia’s freshwater systems is the platypus (Ornithorhynchus anatinus). There is also anunusual group of gastric-brooding frogs of the genus Rheobatrachus, and a large number offreshwater snails (family Hydrobiidae) have very localized distributions within portions of theecoregion. Characteristic fish include one of the world’s largest freshwater species, the MurrayCod (Maccullochella peelii), which reaches lengths greater than 1.5m, and lungfish(Neoceratodus fosteri), which is the only living representative of the Ceratodontidae family.Among many endemic fishes are Murray jollytail (Galaxias rostratus), the primitive spottedbonytongue (Scleropages leichardti), and the migratory Australian grayling (Prototroctesmaraena), which may be the only extant member of its genus and is considered vulnerable.
General threats: Threats to freshwater biodiversity are numerous. Rivers and streams have beenhighly modified by the construction of weirs and dams, channelization, and the removal ofriparian vegetation. Agricultural, urban, and industrial pollution are growing problems in someareas. Introduced species, including fish and aquatic plants, often translocated from otherAustralian regions, are threatening native populations. Aquaculture threatens to further the spreadof non-native species, as well as to release wastewater into freshwater systems. Forest clearing foragriculture and timber production, and subsequent increases in sedimentation, may be one of themost serious problems.
1.2.2 Climate and water resources
An important consequence of the extent of the Murray-Darling Basin is the great range ofclimatic conditions and natural environments, from the rainforests of the cool and humid easternuplands, the temperate mallee country of the south-east, and the subtropical areas of the north-east, to the hot, dry semi-arid and arid lands of the far western plains.
As well as being Australia’s largest river system, the Murray-Darling is also one of the world’smajor river basins, ranking fifteenth in terms of length and twenty-first in terms of area. When allthe rivers, creeks and water courses are plotted on a map, the basin appears to have a mass ofwaterways. However, many of these only carry water at times of flood; for the rest of the time,they are dry. The nature of the Murray-Darling Basin means that, for most of their lengths, mostof the rivers flow over plains. One consequence of this is that their individual courses are far fromsimple, as they meander across their floodplains. The actual course of the Darling is about threetimes as long as the direct distance that is involved. Another consequence of the nature of the
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basin is that the rivers generally have extremely low gradients. As a result, under normalconditions, changes in flow spread down the riverbeds relatively slowly.
While the Darling, Murray and Murrumbidgee are the longest and most important rivers, they arebut three of the 20 major rivers in the basin. Between them, these major rivers have hundreds oftributaries.
1.2.3 Surface water resources
There is considerable variation in runoff from one part of the basin to another, while runoff alsobears little relationship to catchment size. The catchments draining the Great Dividing Range onthe south-east and southern margins of the basin make the largest contributions to total runoff.For example, the Upper Murray, Murrumbidgee, and Goulburn River catchments account for 45.4per cent of the basin’s total runoff from 11 per cent of its area. The Upper Murray catchmentalone accounts for 17.3 per cent from 1.4 per cent of the basin. By contrast, the Darling group ofrivers contributes 31.7 per cent of the basin’s mean annual runoff from 60.4 per cent of its area.The Darling catchment itself accounts for 10.9 per cent of the basin’s area but only 0.4 per cent ofmean annual runoff.
Overall, some 86 per cent of the Murray-Darling Basin contributes virtually no runoff to the riversystems, except during floods. Australia’s climate, compounded by the variability of its rainfall,means that virtually all of Australia’s river systems are subject to considerable variability of flowsfrom one year to the next. In fact, on a global scale, Australia (together with Southern Africa)experiences higher runoff variability than any other continental area. The Murray-Darling Basinis no exception to this, in spite of the fact that much of the river system is now highly regulated.For the Murray and Murrumbidgee, the high and relatively reliable precipitation in their sourceareas means that stream flow is much more reliable than in other parts of the catchment. But evenfor some of their tributaries, there are significant exceptions, notably the Broken and AvonRivers. However, these variations are small in comparison with those of the Darling River and itstributaries. These rivers not only experience massive floods, they can also cease flowing forextended periods. The Darling provides some of the most extreme examples. At Menindee,between 1885 and 1960, the river ceased to flow on 48 occasions. The longest no-flow period was364 days in 1902/03.
Approximately half the surface water management areas are assessed as being developed beyond100% of sustainable yield (Australian Catchment, River and Estuary Assessment 2002, p.233).
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Figure 1.1 Catchment areas in the Murray-Darling Basin
Source: MDBC 2002a, Surface Water
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1.2.4 Water diversions and storage
Given the above potential water resource, it is important to consider the developments associatedin seeking to harvest and store the resource. This has been fundamentally important indetermining the agricultural activity associated with water use.
Of the water that would have originally reached the sea from the Murray-Darling Basin, overtwo-thirds is now diverted from its rivers each year. Mean outflow from the Murray to the sea hasbeen reduced from some 13,700 million m3 per year under natural conditions to 5,750 million m3,or as low as 35 per cent of natural flows according to some sources.
Table 1.2 Runoff, outflows and diversions in the Murray-Darling Basin
Drainage division Mean annualrun-off
(million m3)
Percent meanAnnual run-off
(%)
Mean annualoutflow
(million m3)
Volume diverted(million m3)
Murray-Darling 23,850 6.2 5,750 12,051Source: Australian Water Resources Assessment 2000 (p25)
The mean figures, however, are influenced too much by large floods. The median annual flow tothe sea (i.e. the flow that is exceeded in 50 per cent of years) is now only 21 per cent of thenatural median flow. From a figure of around 3,000 million m3 in 1930, diversions now total over12,000 million m3. On some occasions, as in 1981 and for a number of months in 1995, water hasceased to flow to the sea, though in this case it was due partly to drought conditions. The increasein diversions has been particularly marked since the late 1950s, with over 90 per cent of thediverted water used for irrigation.
The increase in diversions has been primarily due to the expansion of the cotton industry and theuse by growers of large on-farm water storage. Australia has 447 large dams with a combinedcapacity of 79,000 million m3 of water (equivalent to 158 times the volume of Sydney harbour),developed mainly for urban areas, irrigation schemes and hydropower generation. Australia’sseveral million farm dams account for an estimated 9 per cent of the total water stored (AustralianWater Resources Assessment 2000). As a result, there has been much conflict along the Darling,and especially along some of its tributaries, between graziers, conservationists and irrigators.
One very significant result of the reduced flows throughout the basin is that the rivers are now ina state of drought (as defined by river levels) for more than 61 years in every 100, compared with5 years per 100 under natural conditions (MDBMC 1995). This is a particular issue on the lowerreaches of the river system, especially for the Coorong and the mouth of the river Murray. On theother hand, regulation has eliminated most of the extreme low flows, though they are still afeature of the Darling system. Without regulation, the Murray might well have ceased to flowduring the drought of 1982/83.
1.3 Agriculture
1.3.1 General agriculture versus commodity approach
With a view to conserving wetlands and biodiversity by focusing on water use, it is important toconcentrate on particular commodities, rather than on agriculture and water use and waterinfrastructure in general. One concern about focusing on particular crops, however, is that watersavings for example in one commodity may not necessarily produce an environmental benefit if
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they are simply transferred to an alternative commodity, and cannot be secured for environmentalflows. In addition, such an approach may only address a small part of the environmental problemscaused by water infrastructure. That said, a focus on particular commodities of major importanceprovides enormous potential to influence specific outcomes in specific areas, and provide modelsfor best practice across the entire irrigation sector. However, measuring the success of a focus oncommodities may prove very difficult.
The total area devoted to crops in the Murray-Darling Basin is 7,137,303ha, 43.5 per cent of thetotal Australian crop area of 16,404,332ha and 8.4 per cent of the total farm area in the basin.Crops are grown on 31,164 farms, 60.3 per cent of the farms in the basin. The available indicatorssuggest that crop production is relatively more important in the basin than for Australianagriculture as a whole.
A large part of Australia’s major arable farming area, long known as the wheat-sheep belt, islocated within the Murray-Darling Basin. It extends from southern Queensland, through NewSouth Wales and Victoria (to the west and north of the Great Dividing Range) into SouthAustralia. Much of the area has a mean annual rainfall of under 600mm, its unreliable naturebeing a major determinant of crop yield. A large number of crops are grown in the basin, amongthem wheat, barley, rice, oilseeds, cotton, and a number of horticultural commodities. Amongother crops grown are other cereals and pulses (such as lupins, field peas, chickpeas, lentils, mungbeans, faba beans, navy beans, and vetch). Some of these crops are grown mainly for livestockfeed, though others supply niche markets for human consumption, especially in the health foodsector.
Table 1.3 Irrigated crops in the Murray-Darling Basin
Irrigated agriculture in Australia results in significant costs, not least because the bulk of theirrigation water is used for mixed farming and low-value commodities. The situation is furtheraggravated by the fact that a number of the commodities are also inefficient users of water (e.g.pasture, rice). In particular, the irrigation needs for grazing need to be carefully examined if thelarge surface area employed is to be continued, especially since production efficiency is very low(around 1 million litres of irrigation water are required to produce 600–2,000 litres of milk).
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1.3.2 Geographic perspectives in the Murray-Darling Basin
Given the large climatic differences described above, it is important to consider the differencesbetween the southern part of the basin, which is largely winter rainfall dominated, and thenorthern part, which experiences predominantly summer rainfall.
Southern region
RiceRice is the major irrigated cereal crop and is grown almost entirely in the Murrumbidgee andMurray valleys of southern New South Wales. Commercial rice growing started in theMurrumbidgee Irrigation Area in 1924, but the industry’s rapid expansion occurred in the 1970sand 1980s, largely through the increase in the area sown and through improved yields. A recordcrop of 1,284,000 tonnes was harvested in 1995/96. However, there are resource constraints, notonly in terms of the availability of irrigation water, but also because of the environmentalconsequences of the large quantities of water and flood irrigation methods that are used. Up tohalf of the water that percolates down to groundwater from irrigated areas in southern New SouthWales comes from rice production. This represents some 200km3 of water every year. Not only isthis water wasted, it is an undesirable addition to already high water tables. A reduction of deeppercolation from rice cultivation is essential if environmental degradation caused by rising watertables is to be contained. Increased production has to be sought through varieties that give higheryields and require less water.
Fruit treesThe main growing areas are the Riverland (the irrigation areas around Mildura in north-westVictoria and adjoining areas of New South Wales) and the Murrumbidgee Irrigation Area.
GrapesThe major producing areas are in the South Australian Riverland and the Mallee andMurrumbidgee Statistical Divisions.
VegetablesA large number of different types of vegetables are grown in many parts of the basin. Peas, greenbeans, cabbages, cauliflowers, pumpkins and carrots in Robinvale and Griffith, onions in Griffith
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and South Australian Lower Murray, asparagus near Cowra and Jugiong, and Potatoes in theMurray, Murrumbidgee, and Central highlands of Victoria.
Northern region
CottonThe major growing areas are along the Darling River and especially its tributaries in northernNew South Wales and southern Queensland. Limitations on the availability of irrigation water arecontributing to an increase in production of dry-land cotton and also to the spread of irrigatedcotton production to other parts of the basin, such as along the lower Darling and theMurrumbidgee Rivers.
1.4 Irrigation and drainage development
Agricultural holdings in Australia cover an area of 465,953,718ha, of which 2,069,344ha (0.4%)are under irrigation. Of this area, 1,472,241ha (71%) are located in the Murray-Darling Basin.There are 14,743 farms with irrigated crops and/or pastures – 28.5 per cent of the total number offarms in the basin and 47.2 per cent of all Australian farms with irrigation. As a result, it isestimated that agriculture uses 95 per cent of the basin’s available water resources, while forAustralia as a whole this is estimated at 70 per cent.
Four main groups of irrigation scheme can be distinguished, according to their form ofadministration or operation:
• Government established and operated schemes• Government established and now privatized schemes• Privately established and operated schemes• Individually operated schems.
1.4.1 Irrigation methods
The irrigation of crops and pastures is undertaken in many different ways. Irrigation can be theprimary source of water, with the crops more or less totally dependent on irrigation, or it can alsobe regarded as supplementary, providing moisture at critical periods of plant growth and/or as ameans of coping with the vagaries of seasonal rainfall.
A variety of irrigation methods and equipment are employed, and can be summarized as follows:
• Flood: In some cases employing laser land forming technology to ensure level fields forincreased irrigation efficiency, especially for pastures and rice production
• Furrows: The predominant method for horticultural and field crops, and, particularly in theolder schemes, for vines and tree crops
• Sprinklers: There are various types of overhead sprinkler systems, depending on the crops.Systems can be fixed or portable, though the latter can involve considerable labour input;increasing use of under-tree and micro-sprinklers results in much greater water useefficiencies. Employed particularly for tree crops and vines, with centre pivot systems alsoused for irrigating fodder crops, lucerne, vegetables, etc.
• Trickle/drip hoses: Even more efficient, due to direct application of water• Sub-surface drip systems.
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The flood and furrow methods are relatively inefficient, both in terms of application and cropwater use. The area irrigated in this way is declining in both real terms and as a proportion of thetotal area, following the adoption of newer and more efficient methods. Because of theconsiderable capital investment, irrigation methods and equipment cannot be easily changed,except perhaps in replacing flood or furrow irrigation with more sophisticated systems. Theavailable data on the use of the various irrigation methods are limited and problematic. SouthAustralian data indicate that furrow methods predominate in the older areas, while sprinklersystems are found in the more recently established schemes (Smith and Watkins 1993). It can alsobe noted that, in South Australia, overhead sprinklers are now showing some decline after theirrapid expansion in the 1960s, due at least in part to rising water salinity levels.
Figure 1.2 Location of irrigation schemes in the Murray-Darling Basin
Source: MDBC 2002a, Irrigation
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1.4.2 Environmental impacts of water diversions and storages
Impoundments, surface water abstraction and river regulation associated with water resourcedevelopment are significant drivers of riverine ecosystem condition. These same drivers affect thehealth and condition of freshwater fish communities, many of which are known to be migratoryand rely on hydrological cues for breeding.
To date, WWF has focused on impacts from water storages generally, and has soughtunsuccessfully to have various threatening processes notified under environmental protectionlegislation. These processes are: changes to natural flows, changes to natural quality, changes tonatural temperature, barriers to fish passage, introduced species, and removal of large woodydebris (for habitat). WWF has, however, managed to ensure the listing under legislation of oneaquatic community of the lower Murray, Murrumbidgee and Tumut Rivers which would mostlikely become extinct if the threats were to continue.
It is difficult to match the particular agricultural commodities to these impacts, and also difficultto identify how changes in the production of particular commodities will address threats tobiodiversity. This is because many of the threats relate to the way water is collected anddistributed. For example, the changes to natural flows, natural temperatures and barriers to fishhabitat are due to dams which make water available for irrigation of a variety of crops, as well asfor town water supplies and in some cases hydroelectricity generation. Changes to natural qualitycan come from irrigation as well as non-irrigation sources, and identifying the particularcontribution of each is difficult and specific to a particular valley. The means by whichenvironmental flow increases are to be secured is the subject of much debate. Water efficiencysavings in particular industries may not lead to increases in environmental flows unless they arespecifically purchased for the environment. Water efficiency gains may be used to increase thetotal amount of irrigated area. Also, in the particular circumstances of many Australian rivers,where inefficient water users have been operating for a long period, moving to increased wateruse efficiency can have a significant impact on return flows from farms.
Further, there has been extensive debate about the means by which improvements in particularcommodity practices will lead to environmental improvements. In some cases, the benefits can bemore clearly linked to practices. Reduction of nutrients and chemicals entering waterways shouldprovide a clear linkage to improvement in particular water quality parameters, however overallriver health is dependent also upon riparian zone health, and the quantity, timing and temperatureof flows. Again, because of these complexities, determining the extent to which improvementsare sought in particular commodity groups and the potential for these to lead to significant healthimprovement is difficult. Despite this, there have been several attempts to determine thecontribution that particular industries can make in particular situations. One example is thecomplex and important ‘Living Murray’ project developed by the Murray-Darling BasinCommission (MDBC 2002b).
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Table 1.5 Inter-basin transfers of water involving the Murray-Darling Basin
From river basin To river basin Estimated quantity(million m3)
Remarks
Transfers into the Murray-Darling BasinBrisbane Condamine 4 Perseverance Ck diversion for Toowoomba water
supply (to be augmented by Cressbrook Creek Dam) Snowy Upper Murray 580 Snowy Mountains Scheme (additional water made
available through regulation) Snowy Murrumbidgee 550 Snowy Mountains scheme (additional water made
available through regulation) Glenelg Wimmera-Avon 76 Rocklands Dam supplies some of the water for the
Wimmera Mallee Stock and Domestic Scheme Transfers out of the Murray-Darling BasinMacquarie Hawkesbury 14 Fish River water supply scheme Goulburn Yarra 13 Silver-Wallaby Creek aqueduct for Melbourne water
supply Lower Murray South Australian
Gulf DrainageDivision
350 Water pumped from the Murray River for watersupply to Adelaide and numerous other parts ofSouth Australia
For Australia as a whole, recent studies have indicated that over 20 per cent of the nativevegetation has been cleared for agricultural and other purposes, compared with previous estimatesof 6–8 per cent. The figure rises to 52 per cent in what has been termed the ‘intensive land usezone’ of the continent, which includes much of the basin (Graetz et al. 1995).
At least half of the Murray-Darling Basin’s pre-European settlement vegetation cover has beenremoved, and many new plants and animals have replaced native species. In the arid and semi-arid areas in particular, many native species are not regenerating. Many have been lost, not leastthose of native grasslands. There is little wilderness of high quality remaining in the Murray-Darling Basin.
Over the period of European settlement, the basin has undergone some of the most extensive anddramatic vegetation changes in Australia. Significant among these has been the clearing ofeucalypt woodland and shrubland in the drier areas and their replacement by crops and pastures,notably in what has long been known as the wheat-sheep belt that stretches from south-eastQueensland through New South Wales and northern Victoria into South Australia. Over largeareas, the native vegetation, both woodland and shrubland, has been thinned rather than cleared,again in the interests of agricultural activities.
Quite apart from the clearing of native vegetation, land use is constantly changing. Theintroduction of new crops and new farm management practices, for both crops and livestock,means that agricultural land use changes frequently. Crops such as cotton, rice, canola, andsunflowers are evident in terms of land use and their visual impacts. Agricultural and pastoralland is taken for urban development, with Canberra providing perhaps the best illustration withinthe basin.
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Table 1.6 Changes in natural vegetation in the Murray-Darling Basin
Mangroves, tidal mudflats, samphires, claypans,salt lakes, bare areas, sand, rock, lagoons,freshwater lakes and reservoirs
673,220 636,496 36,724 5
Source: Australian Catchment, River and Estuary Assessment 2002 (p229)
1.5.1 Erosion rate and sediment
Most of the east and south has undergone a two to fivefold increase in rate of hill-slope erosion.Some dry-land agricultural areas in the upper catchments of southern and eastern river basins andon the lowland sandy soils of cleared mallee areas in the south-west are experiencing hill-slopeerosion rate increases of between 10 and 30 times natural rates (Australian Catchment, River andEstuary Assessment 2002, p231).
1.5.2 Nutrient loading
River basin nitrogen loads are estimated to have doubled on average compared to pre-Europeansettlement levels. Phosphorus loads are estimated to have tripled on average, due to an increasedpercentage (77%) of the phosphorus load being transported in association with fine sediment.Approximately half (52%) of the nitrogen load is transported in association with fine sediment,highlighting the role of fine sediment as a key transport mechanism for nutrient loads.
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Figure 1.3 Land use in the Murray-Darling Basin
Source: MBDC 2002, Land Use
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1.5.3 Salinity
Land salinization occurs naturally in parts of the Murray-Darling Basin in the form of salineseepages and scalds. The concern here, however, is with secondary or induced salinizationresulting from European-type land use activities.
In the basin’s irrigation areas, the problems that can result from the removal of native vegetationhave been compounded by the application of large additional quantities of water, very oftenwithout any drainage facilities to remove excess water. Thus, over large parts of most of thebasin’s irrigated lands, water tables are now less than 2m from the surface, resulting in bothsalinization and waterlogging. In 1987, it was estimated that 96,000ha were affected by salinesoils and 560,000ha had water tables within 2m of the surface, with the latter rising rapidly inmany areas. By 2040, 1.3 million ha of irrigated land is expected to be saline or waterlogged as aresult of high water tables.
A range of measures is being undertaken to combat rising water tables and salinization inirrigation areas. These include surface and sub-surface drains, groundwater pumping, pumping ofsaline groundwater into evaporation basins for later collection and disposal, water harvesting(especially of drainage water), in some cases disposal of saline drainage water to the MurrayRiver, tree planting, and adopting a holistic approach to farm planning and management,especially in terms of water use management and coping with saline environments (‘living withsalt’).
Water resources at riskThe most significant off-site impact of dry-land salinity is the salinization of previously freshrivers. This affects the supply of drinking and irrigation water, with serious economic, social andenvironmental consequences for rural and urban communities.
A salinity audit by the Murray-Darling Basin Commission suggested that in the absence ofremedial action, the median salinity in the Murray River at Morgan was estimated to increase byabout 25 per cent over the next five years as a result of increased salt inflows from irrigation anddry-land districts (MDBC 1999). Stream salinity in the Murray exceeds World HealthOrganisation levels for potable water for about 10 per cent of the year. Salinity levels in theMurrumbidgee River are increasing at between 0.8 and 15 per cent each year, depending onwhere measurements are made. The audit also suggests that in the upper basin, the Macquarie,Namoi, Bogan, Lachlan and Castlereagh Rivers will exceed the 800EC units threshold for waterwithin the next 50 years. Some will also exceed the 1500EC units threshold for irrigation within100 years.
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Table 1.7 Potential effect of current land use on the spread of dry-land salinity by 2050
Source: Australian Dryland Salinity Assessment 2000 (p 27)
Costs of salinityEstimation of the costs associated with losses in biodiversity is complex and methods are not welldeveloped. Preliminary results from a recent study carried out for the Murray-Darling BasinCommission in eight priority catchments indicate that salinity costs to farmers, local governmentand government agencies are approximately AU$251 million a year.
Table 1.8 Total equivalent costs in eight priority catchments in the Murray-Darling Basin
Lower estimate(AU$million/yr)
Upper estimate(AU$million/yr)
Best estimate(AU$million/yr)
Local government - - 14.69Households 41.03 139.23 90.13Businesses 8.45 8.96 90.13Sate government agencies and utilities - - 16.31Environment ? ? ?Agricultural producers - - 121.80Total 202.28 300.99 251.64Source: Australian Dryland Salinity Assessment 2000 (p14)
1.5.4 Economic and social impacts
The gradual long-term movement of labour out of agriculture and the declining proportionalcontribution of agriculture to total economic growth bring with them significant changes in thesocial structure of rural areas. Significant changes include: a declining number of farms, feweryoung people entering agriculture, increased dependence on off-farm income, ageing of the farmpopulation, and continuing decline in the size of Australia’s farm population. Demographicmodelling of future structural changes in Australian agriculture projects that there will be acontinuing decline in the size of Australia’s farm population. Two scenarios present themselves:
• A 30 per cent decline in farmer numbers by 2020 and a further increase in median farmerage, peaking in 2001 – based on the behaviour of farmers during the period 1991–1996, withpoor prices for farm commodities
• A 55 per cent decline in farmer numbers with little increase in current median age – a fasteradjustment scenario based on behaviour during the period 1986–1991, in which commodityprices were generally higher (Australian and Natural Resource Management 2002, p79)
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1.5.5 Future of irrigation
The factors that will play a role in the future of irrigation in the Murray-Darling Basin can bedivided into two categories: economic and environmental.
The economic issues comprise the price of water, water rights, and the viability of much ofirrigated agriculture. Too many low-value commodities are currently being produced byinefficient irrigation methods, while many farms are too small in area and income. Theseagricultural systems and current water prices cannot support the cost of rehabilitation of watersupply schemes and the installation of drainage systems.
The environmental factors involve a complexity of land and water salinization issues, the majorproblem being the increase in water demands by the domestic and industrial sectors. This willrequire irrigated land to be taken out of production.
The Australian Bureau of Statistics (ABS) has released estimates based on surveys of water useduring 1996/97. These are presented in Table 1.9. ABS estimated that 68,703km3 of surface andgroundwater was extracted from the environment in this period. The net amount of water usedwas 22,186km3, allowing for return flows, mainly from hydropower. ABS also estimated thatover the four years from 1993/94 to 1996/97 total net water consumption rose by 19 per cent,from 18,575km3 to 22,186km3. A large part of the rise was accounted for by the agriculturesector, particularly pastures. It should be noted that there is great variability in annual water usewithin the Murray-Darling Basin, and the early 1990s were a period of drought, reduced storage,and reduced allocations. Hence, the data for 1993/94 to 1996/97 overstate the long-term trend.
Table 1.9 Australia’s mean annual water use by category in 1996/97
State Irrigation(million m3)
Urban/industrial(million m3)
Rural(million m3)
Total use(million m3)
New South Wales 8,643 1,060 305 10,008Victoria 4,451 987 339 5,777Queensland 2,978 1,052 561 4,591Western Australia 710 1,027 59 1,796South Australia 819 292 53 1,164Tasmania 276 186 9 471Northern Territory 53 87 39 179Australian CapitalTerritory
5 63 4 72
Total 17, 935 4, 754 1,369 24,058Source: Australian Water Resources Assessment 2000
Table 1.10 Change in mean annual water use by category between 1983/84 and 1996/97
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2 CONCLUSIONS FOR THE MURRAY-DARLING BASIN
2.1 Irrigated agriculture
The Murray-Darling Basin is one of the largest river basins in Australia and, containing a numberof WWF Global 200 ecoregions, is a major focus of WWF’s Living Waters Programme. Thebasin covers a number of states and the entire Australian Capital Territory. This study hasassessed the size of the surface areas of each of these states in the basin. Data were collected onthe major irrigated crops, their water requirement per crop, and the area under cultivation. Alldata are available from the Murray-Darling Basin Commission website.
Since more than 71 per cent of the irrigated area of Australia is located in the Murray-DarlingBasin, water consumption per crop in the basin will be considered as representative for Australiaas a whole.
One crop, however, that is not grown in the basin is sugarcane, which is grown mainly inQueensland and covers an area of 172,267ha (Dunlop 2001). Total water consumption for thisarea is estimated at 1.2km3, which ranks sugarcane among the top four water-consuming crops inAustralia.
Table 2.1 Water consumption by four major crops in the Murray-Darling Basin
From Tables 2.1 and 2.2 it can be concluded that the largest water-consuming crops, pasture andrice, also have the lowest value per unit of water, with sugar and cotton in third and fourth place.Where feasible, conversion to fruit and vegetable cultivation should be pursued, as this willreduce water use and provide higher income per unit of water.
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2.2 Future water demand
IWMI Working Paper No.32 Water for Rural Development was used to collect information on thefuture water situation. The general conclusion for Australia is that there will be economic waterscarcity – i.e. primary water supply (PWS) less than 60 per cent of the potential utilizable waterresources (PUWR) – with a requirement to increase PWS by more than 25 per cent over currentlevels.
An interesting development in Australia is that the total cereal area will not change; thus, thedecrease in rain-fed cereal area is compensated by an increase of 490,000ha of irrigated land. Asimilar development can be observed in Thailand, the major rice producer of South-East Asia.
